1. Field of the Invention
The present invention relates to a glass antenna attached to a rear window glass of a vehicle such as an automobile for reception of AM radio broadcast waves, FM radio broadcast waves and TV broadcast waves, and particularly to such a kind which is suited for reception of FM radio broadcast waves and AM radio broadcast waves.
2. Description of the Related Art
In order that the sight of the driver is not obstructed by a glass antenna, it is a usual practice to attach the antenna not to a windshield but to a vehicle rear window. In recent years, a number of glass antennas for FM radio broadcast waves and glass antennas for AM radio broadcast waves have been proposed and a number of applications relating to such glass antennas have been filed. One of them is a glass antenna including a conductive strip perpendicular to heating strips of a defogging heater element and connected to same and another one is a glass antenna including an antenna element which is disposed in a space above the heater element and has a portion disposed so as to intersect at right angles the heating strips of the heater element while being connected to same, those antennas being disclosed in JP 56-42401. Another one of them is a glass antenna including a vertical conductive strip extending along a bus bar of a defogging heater element and a short horizontal strip disposed in a space above the defogging heater element, this kind of antenna being disclosed in JP 62-123803 and JP 3-85004 which were assigned to the same assignee of this application.
However, the gain of the glass antenna disclosed in JP 56-42401 in receiving FM radio broadcast waves is not sufficiently large considering the fact that it occupies almost all of the space above the defogging heater element, though the antenna can attain a certain measure of gain in receiving AM radio broadcast waves.
Further, the glass antenna disclosed in JP 62-123803 occupies only a small area of the space above the defogging heater element but is incapable of attaining a sufficiently large reception gain in receiving broadcast waves in a considerably wide band extending from AM radio broadcast band to TV broadcast band.